While many would assume Dumoulin's inability to conquer a knee injury in time for the Grand Départ from Brussels on July 6 would allow the Australian free-reign to target stage victories and a second green jersey after his points classification win in 2017.
However, Matthews has revealed he had spent the first half of 2019 training to be as useful as possible to Dumoulin, who was set to try and go one better than his second place finish in last year's Tour.
Matthews had been training for the climbs and the stage two team time trial, telling Dutch broadcaster NOS: "I’ve been making sure I can climb really well, making sure I can do a really good TTT to support him as best as possible. It’s definitely hard to take in the news."
Despite the 28-year-old admitting that there a number of stages that would suit him, Matthews says he will go to the Tour having done little preparation for any of them: "I haven’t done any sprint training or any training that was preparing myself for my stages, and there are quite a lot of stages that do suit me.
"It’s massively disappointing, obviously. I don’t know what to do now, I’m totally confused. Even the plans to go up to Livigno from here to make sure I was really ready in the mountains to support Tom.
"It’s just a massive disappointment, to be honest, and I don’t know where to go from here."
Matthews also revealed that Sunweb's plans going into 2019 were Dumoulin or nothing, with team manager Iwan Spekenbrink telling the entire roster that they "shouldn’t have any ambitions ourselves – it’s just everything for the yellow."
This put a dent in Matthews' Giro d'Italia 2019 plans, where had hoped to compete for the points classification, but this ambition was ended after it was decided Dumoulin would ride the Giro as well as the Tour. The Dutchman eventually abandoned the Italian Grand Tour on stage five after a crash the previous day which gave him the knee injury that continues to thwart his season.
It has also been announced that Dumoulin will miss the Dutch national championships this week, where he has won the time trial three times, in 2014, 2016 and 2017.
But who will replace Dumoulin at the Tour? Sunweb don't have another Grand Tour contender up their sleeve but do have 2013 Tour stage winner and yellow jersey-wearer Jan Bakelants as a potential option.
Dutch newspaper Nieuwsblad reports that Sunweb are considering four options for the spare spot on the squad, with sprinter Cees Bol, climber Martijn Tusveld and all-rounder Roy Curvers all also being considered.
Bakelants would not be coming into the French Grand Tour fresh, having raced the Giro followed by the Hammer Series and the ZLM Tour, but the Belgian said: "Sometimes the Tour can be better than expected if you don't have the ideal preparation. In 2013 I only went in the final selection."
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